Tiago signed for Chelsea on 20 July 2004 for a €15 million fee,[1] becoming José Mourinho's sixth signing that season (this included three other Portuguese players). Having missed the first game of the 2004–05 campaign he soon became an important member of his new team, scoring on his away debut against Crystal Palace on 24 August;[2] he also scored a long-range goal in Chelsea's 3–1 win over Manchester United on 10 May 2005, after already having won the Premier League title.[3]

Tiago was a regular for Chelsea that season, having only missed four games in the league. He ended the season successfully as a firm fixture in the Blues' midfield three, making 51 appearances in all competitions and scoring four goals as the club also added the season's Football League Cup. However, despite his initial success, the following campaign saw the arrival of Michael Essien from Olympique Lyonnais, which limited his first-team chances; during his time at Stamford Bridge his loss percentage in the league was 2.94%, just once in 34 appearances (a 0–1 loss at Manchester City on 16 October 2004), which was the lowest in history for any player having appeared at least 20 times.[4]

In late August 2005 Tiago signed for Essien's former club on a four-year contract, for a €10.1 million transfer fee.[5][6] Mourinho later confessed in an interview that letting him go was "a big mistake."[7]

On 17 June 2007, Lyon president Jean-Michel Aulas confirmed that Tiago's departure from Lyon was imminent with both Juventus F.C. and A.C. Milan reportedly after his signature. He officially signed for the former on 21 June 2007, for a €13 million fee.[8] His performance in the 2007–08 season was criticised, however, as Goal.com describing him as the third biggest flop of the season.[9]

The start of 2008–09 season gave Tiago an opportunity to return to the Premier League in the form of year long loan offer from Everton. Juventus agreed to the deal but Tiago refused their terms, favouring to stay in Italy instead.[10] The negotiations between the player and the club had a violent end when Tiago forcibly locked Juventus president Giovanni Cobolli Gigli inside a toilet stall – the chairman was finally rescued by captainAlessandro Del Piero, more than an hour later;[11] after a difficult first season he eventually established himself in Claudio Ranieri's side but, in November 2008, against Inter Milan, he was stretchered off the pitch with a serious knee injury just several minutes into the match, and was sidelined for almost two months.

Tiago returned to the bench for the January match against S.S. Lazio, but found himself down the pecking order as Cristiano Zanetti, Mohamed Sissoko, and emerging youngster Claudio Marchisio were Ranieri's preferred centre midfield pairing. Following injuries to Sissoko and later Marchisio he was back in the starting XI, but his return was soured by a straight red card in the Derby d'Italia fixture in April (1–1 home draw).

The first half of the 2009–10 season was one to forget for Tiago. With the arrivals of midfielders Diego and Felipe Melo, coupled by his slight dip in form, his appearances were again limited; under Ciro Ferrara he was relegated to the bench once again, only making seven Serie A appearances.

After helping the Colchoneros to the domestic cup final – he was cup-tied for the Europa League – a new loan deal was arranged with Juventus.[15] Again, he played in significantly more minutes than García as Atlético finally qualified to the Europa League, and added four goals in La Liga, including a brace against Málaga CF in a 3–0 away win, both goals coming from headers.[16]

On 21 July 2014, aged 33, Tiago renewed his contract with Atlético for two seasons.[19] On 13 September he put the visiting team ahead at Real Madrid after heading home a corner kick from Koke, in an eventual 2–1 win. In the reverse fixture on 7 February 2015, he opened the scoring in a 4–0 success.[20] Eighteen days later, he was sent off as Atlético lost 0–1 away to Bayer Leverkusen in the first leg of the last 16 of the Champions League.[21]

Tiago's performances in Portugal's youth teams eventually earned him his senior debut against Scotland in a November 2002 friendly. He went on to seal a regular berth in the squad and was included in the 23-man list for UEFA Euro 2004, although he did not play in the finals.

Moving to France proved crucial in international selection as Tiago's strong form at Lyon afforded him a place in Portugal's well-established midfield. His contributions aided the national team in its quest for qualification for the 2006 FIFA World Cup, and he appeared in five matches in the tournament held in Germany as Portugal reached the semi-finals, losing to France.

Tiago scored his first goal for the national team in March 2007, in a Man of the match display away to Serbia (1–1). He was, however, overlooked, for Euro 2008's final squad.

After the World Cup, Tiago officially quit the national team citing personal reasons, and also to "make room for opportunities for younger players," ending his international career with 58 caps and three goals.[23] On 3 October 2014, however, after an absence of almost four years, he was called up by new manager Fernando Santos for a friendly with France and the Euro 2016 qualifier against Denmark.[24] He was sent off for two bookings on 13 June 2015, as Portugal won 3–2 away to Armenia in another qualifier.[25]